Chinese Rover Finds New Volcanic Moon Rocks

The Chinese lunar rover, Yutu, photographed by its lander Chang'e-3, after the lander touched down in Mare Imbrium, a giant impact basin that had been filled by successive lava flows. Credit: CNAS/CLEP

A Chinese rover is currently engaged in the analysis of lunar rocks.

Two years ago, a lunar mission went to the moon and it was of Chinese origin. Called the Chang’e-3, it landed on the northern area which consisted of the Imbrium basin. This is filled with lava. The landing site was a sight to see.

The mission landed on a smooth basalt plain. Nearby was an impact crater (named the Zi Wei). Ever since the Apollo program ended, America has carried out its explorations from an orbital distance. But the Chinese are landing rovers on the moon.

Orbital sensors can detect regoliths that surround the moon. Regoliths are a mixed bag and difficult to analyze. In case of the Chang’e-3, the landing was on a young lava flow.

So the regolith layer was not mixed. The ground truth of the remote sensing was thus found. The moon’s upper crust is less uniform than the earth. And the moon’s volcanoes have changed with time.

The moon has been postulated to have been formed via a collision between a Mars-sized body and the earth. The moon was molten at the beginning and then cooled off to form what we see today.

The volcanic eruptions were due to a remelting that took place later on. Radioactivity had a lot to do with it too. The Apollo and Luna missions sampled the basalt from the volcanic areas.

These volcanoes erupted some 3 and 4 billion years ago. The basalt samples returned by the Apollo and Luna missions had either a high titanium content or a low titanium content.

Any values in between these two extremes were lacking. Measurements made from the Yutu rover show that the basalt contains intermediate amounts of titanium and high iron content. Titanium is used to measure the levels of volcanic activity on the lunar surface.

"We now have 'ground truth' for our remote sensing, a well-characterized sample in a key location," Jolliff said. "We see the same signal from orbit in other places, so we now know that those other places probably have similar basalts."

The percentage of the titanium in the basalt shows the conditions of the magma in the earlier molten times. Minerals solidified from the magma in a certain manner.

Two magnesium and iron rich minerals solidifed first. They are denser and sink to the bottom of the magma. Another mineral which is lighter than the magma floats on top of it.

This process of separation via differentiation is responsible for the various layers of the moon. As for the titanium, it becomes the mineral ilmenite. The Yutu rover will yield important data about the moon’s history in terms of its structure.

"The diversity tells us that the Moon's upper mantle is much less uniform in composition than Earth's," Jolliff said. "And correlating chemistry with age, we can see how the Moon's volcanism changed over time."